A typical train includes one or more locomotives pulling a plurality of load cars. Each vehicle in the train includes a plurality of metal wheels that roll along the metal rail as the train is propelled along the track. The rolling contact between the wheel and the rail provides an efficient mode of transportation, particularly for heavy loads. Proper interaction between the wheel and the rail is critical for safe, reliable, efficient operation of the train.
A rail includes a bottom mounting flange, a top railhead that makes contact with the vehicle wheel, and a flange interconnecting the flange and the railhead. A vehicle wheel includes a center hub mounted onto the vehicle axle, a plate extending outwardly from the hub, and an outer rim surrounding the plate for making contact with the rail. The rim includes an outside diameter tread that may be flat or tapered and a flange extending outwardly from a back side of the tread. The tread rides along a top surface of the railhead for supporting the vertical weight of the vehicle. The flange extends along and makes contact with a side of the railhead for providing lateral support to allow the wheel to follow along the path of the railhead. Flanges are provided on only one side of each wheel along an inside of the rail. As a train negotiates a curve in the track, the flanges of the outer diameter (high side) wheels provide the lateral forces for turning the train.
Rail vehicle wheels suffer wear over time due to their contact with the rail. The treads wear as a result of their contact with the top of the rail, particularly in the event of the wheel slipping with respect to the rail during acceleration or braking events. The wheel flanges will wear due to their contact with the inside surface of the railhead, particularly on curves and through switches. It is known in the art to provide lubrication between the wheel and the rail in order to reduce wheel wear and to provide more efficient movement of the wheel over the rail. Lubrication may be provided on the top of the rail to reduce rolling friction at any location. Flange lubrication systems are especially useful in curved areas of the track where the forces between the railhead and the flange are at their maximum. Both on-board and wayside lubrication systems are used. On-board systems are useful for applying lubricant at any location along a rail line. Wayside lubrication systems are typically installed only at curved locations of the track. In some situations, it is desirable to apply lubrication between the wheel and the flange in order to minimize wear of the flange, while at the same time it is undesirable to apply lubrication to the top of the rail because of the reduction in traction that may be generated against a lubricated rail. In general, it is desired to achieve adequate lubrication while minimizing the amount of lubricant used so that the location of the lubricant can be precisely controlled, the cost minimized, and the impact upon the surrounding environment abated.
Numerous patents have issued for systems that control the amount, timing and location of lubrication applied between a wheel and a rail. U.S. Pat. No. 6,182,793 describes an on-board lubricant delivery system that changes the rate of application with the speed of the train. U.S. Pat. No. 6,009,978 describes an on-board lubricant delivery system that applies lubrication only when the rail vehicle is on a curved section of track. U.S. Pat. No. 5,896,947 describes an on-board lubricant delivery system that applies flange lubrication at the front of a locomotive and also applies both flange lubrication and top-of-rail lubrication at the rear of the locomotive. This system controls the rate of lubrication in response to train speed, track curvature, trailing tonnage, temperature, direction of travel, status of braking, and high rail verses low rail. U.S. Pat. No. 6,199,661 describes a computer-controlled on-board lubrication system that applies a lubricant only in a quantity that will be consumed by the time the entire train has passed.
Wayside lubrication systems are commonly activated by the weight of a passing vehicle. The weight of the vehicle is sometimes used as the source of energy for pumping the lubricant, as described in U.S. Pat. Nos. 4,334,596 and 5,076,396. Known wayside lubricating systems often dispense an inappropriate amount of lubrication and/or dispense lubrication when it is not beneficial. U.S. Pat. No. 4,856,617 describes a wayside lubricating system that incorporates a test cycle to provide compensation for changes in lubricant viscosity as a function of temperature. However, further improvements to wayside lubrication systems are needed.